The roof of a male midshipman fish's rocky shelter has been lifted away to reveal its cavelike dwelling at low tide. The male is guarding a nest of month-old larvae, each less than an inch (2.5 centimeters) long.

Males that get distracted risk having the eggs fertilized by smaller and less vocally talented males that can't attract females of their own. If a male catches another trying to sneak into its turf, it will grunt and growl using its swim bladder.

A July 2008 study shows that the noisy fish use the same brain region as other vertebrates to control their vocalizations. But groups of animals have evolved to use different muscles to make sounds, noted University of Chicago biologist Melina Hale. Birds, for example, use an organ called the syrinx, while mammals use their larynxes.

"There's this fundamental similarity in brain circuits," Hale said, "but then there's this beautiful diversity on top of it."